Lactobacillus reuteri

Written by: Kari Raman, PharmD, RPh
Published April 23, 2023

Lactobacillus reuteri is a type of bacteria naturally found in the human gastrointestinal tract, as well as in the mouth, urinary tract and breast milk. It is one of the many probiotic species that have gained popularity in recent years for their potential health benefits, and a lot of probiotic blends contain it. As a pharmacist, I am often asked about the benefits of L. reuteri, if it’s a good probiotic, if a  supplement that has it is worth it – all the standard questions on probiotics. (To learn more about how probiotics are named, please visit my probiotic species page, and you can learn about the genus Lactobacillus here.)

There are numerous clinical studies and research articles examining the potential benefits of Lactobacillus reuteri. As a pharmacist, I like the probiotics that have the most research, since it’s easiest for me to understand what they can and can’t do, and the science makes it easier to recommend the right ones for the right people.

Of course, if you have any serious medical conditions or any chronic health problems see your doctor before turning to a supplement. 

What does Lactobacillus reuteri do?

Research has suggested several possible health benefits associated with Lactobacillus reuteri, such as promoting gut health, improving immune function, supporting oral health, and more. However, it is important to note that individual results may vary depending on factors like the specific strain, dosage, and each person’s unique situation. Always consult your primary care physician if you have any serious health concerns.

Clinical trial summary

Numerous clinical trials have been conducted to study the potential benefits of L. reuteri. The gold standard for these trials is the “double-blind placebo-controlled” study, where some participants receive the probiotic while others receive a placebo, and neither the participants nor the researchers know which group is which. The problem with a lot of probiotic research is that it’s not always done as a double blind study; when I cite studies I try to refer to double blind ones, but they are just not always available. 

Here are some findings from clinical trials and studies that suggest how L. reuteri may work as a probiotic:

Promoting gut health: L. reuteri helps maintain a healthy balance of gut flora by competing with and inhibiting the growth of harmful bacteria. It does this by producing antimicrobial substances that create an unfavorable environment for pathogenic bacteria. For example, this study published in Frontiers of Microbiology explains how it “can produce antimicrobial molecules, such as organic acids, ethanol, and reuterin. Due to its antimicrobial activity, L. reuteri is able to inhibit the colonization of pathogenic microbes..” So it may be able to help make your overall digestive system better balanced and healthier – of course, not every probiotic can help every specific person, but it’s a good one to consider. Especially since it’s in so many different probiotic brands.

Enhancing immune function: Some studies suggest that L. reuteri may help support the immune system by interacting with immune cells and enhancing their activity. This can improve the body’s ability to respond to infections and other challenges. Believe it or not, there is a lot of research starting to show the connection between the gut microbes and the immune system. I wouldn’t call this all ‘figured out’ yet – there is still a lot we don’t know about how the immune system works with the microbiome, but what is clear is that keeping your digestive system healthy is good for your immune system. 

Reducing symptoms of gastrointestinal disorders: Clinical trials have shown that L. reuteri may help alleviate symptoms associated with gastrointestinal disorders such as irritable bowel syndrome (IBS), functional abdominal pain, and constipation. However, many of these studies are small and don’t clearly show improvement, so it’s hard to say that this particular probiotic will help with any specific digestive disorder. It’s probably not the one I would first recommend for IBS, for example. 

Supporting oral health: L. reuteri has been shown to help reduce plaque formation and improve overall oral health. Some studies have even suggested it may help prevent tooth decay and gum disease. I would say that this is an emerging area of research, so I’d continue to focus on brushing and flossing! 

While there is a growing body of research supporting the potential benefits of L. reuteri as a probiotic, more studies are needed to determine the optimal strains, dosages, and duration of treatment for different conditions. One condition where more research is needed is if this particular strain is helpful for stomach issues many women face during their menstrual cycle – read more on my article about proboitics and your period. Always consult a healthcare professional before starting any probiotic supplementation, especially if you have a weakened immune system or other underlying health conditions.

If you are interested in learning about how long it takes for probiotics to work, visit my article that breaks down how long it may take to see a positive impact based on various conditions. 

How do you take Lactobacillus reuteri?

Follow your doctor’s instructions, but generally, people taking L. reuteri for digestive issues should take 1 billion to 10 billion colony-forming units per day (CFUs – what is a CFU you ask? Check out my handy article on CFUs explaining this odd form of supplement measurement!). Depending on the probiotic product, this could be one or several pills per day.

Can you take L. reuteri every day?

Yes, Lactobacillus reuteri can generally be taken daily as a probiotic supplement or consumed through fermented foods containing live cultures, such as yogurt, kefir, or certain types of cheese. This is why it’s in many of the probiotic blends – generally, it can be taken regularly by healthy people, and again there are some studies that suggest it can help with a variety of conditions.

Always follow the recommended dosage instructions provided on probiotic supplements; and consult your doctor before starting any supplement. And remember, many of the health problems we talk about in this article can have serious underlying causes, so it always makes sense to see your primary care physician.

Lactobacillus reuteri FAQ’s

Is Lactobacillus reuteri naturally found in the human gut?

Yes, Lactobacillus reuteri is a naturally occurring bacteria in the human gut, playing a role in maintaining a healthy balance of gut flora. It can also be found in the mouth and other parts of the gastrointestinal tract, as well as the urinary tract. 

Is Lactobacillus reuteri in yogurt?

Some yogurts may contain Lactobacillus reuteri, but not all. Check the label for “live and active cultures” and look for specific mention of L. reuteri as an added probiotic. Unfortunately not many yogurts really list if they have any particular bacteria in them, so this might be hard. If you are really, really dedicated to getting Lactobacillus reuteri in your yogurt, here is a recipe that I found (but haven’t tried!)

Is Lactobacillus reuteri in cheese?

  1. L. reuteri may be present in certain types of cheese, particularly those made with raw milk or cheeses that are specifically produced with added probiotics. However, the presence of L. reuteri in cheese is not guaranteed, and it is best to check the label for information on live cultures. Again, I’m not really sure how to find a cheese that contains it without calling a producer.

Does Lactobacillus reuteri produce lactic acid in the gut?

Yes, Lactobacillus reuteri is a lactic acid-producing bacteria. It generates lactic acid as a byproduct of its metabolism, which can help create an unfavorable environment for pathogenic bacteria, supporting gut health.

Does Lactobacillus reuteri have a positive impact on gut health as a probiotic?

Several studies have demonstrated the potential benefits of L. reuteri as a probiotic in supporting gut health. By producing lactic acid and other antimicrobial substances, L. reuteri can help maintain a healthy balance of gut flora and inhibit the growth of harmful bacteria. I listed some studies above in the clinical trial section that might be helpful to learn more.

Does Lactobacillus reuteri improve digestive health?

Research suggests that L. reuteri may improve digestive health by alleviating symptoms of gastrointestinal disorders, such as constipation, diarrhea, and irritable bowel syndrome. I listed some studies above in the clinical trial section that might be helpful to learn more. I do think some of this research is light, so it’s not the first bacteria I would turn to for digestive health. However, as with any probiotic, results may vary depending on individual factors, strains, and dosages.

How do I buy L. reuteri?

This bacteria is in a number of good supplements. One that I’ve reviewed is Microbiome Plus+.

Does Lactobacillus reuteri improve the immune system?

Some studies have shown that L. reuteri may help enhance immune function by interacting with immune cells and modulating their activity. This can improve the body’s response to infections and other challenges.

Is Lactobacillus reuteri a common cause of UTIs?

No, Lactobacillus reuteri is not a common cause of urinary tract infections (UTIs). In fact, some research has suggested that L. reuteri may help prevent UTIs by maintaining a healthy balance of bacteria in the urinary tract and inhibiting the growth of harmful bacteria.


Pharmacist Kari Raman

I’m Kari Raman PharmD, RPh, and I am a licensed, practicing pharmacist. I hold a Doctorate in Pharmacy from The University of the Pacific, and I’ve served patients in retail, compounding and hospital pharmacies.

Probiotics are confusing!

One of the most common questions I get asked by patients is about probiotics. And the truth is, probiotics are not as well understood by the healthcare community as they should be.

So I’ve been reading a lot of probiotic clinical trials, and sharing what I’m learning here.

I hope Pharmacist Probiotics helps you find out if there is a type of probiotic that works for you!